In such a heating apparatus which is already known from practice, circuit boards, in particular, are supplied to the feed portion of the heating apparatus manually or automatically in continuous succession. The feed portion is followed by a heating portion. In the heating portion, the circuit boards are transported successively in a vertical conveyor upwards to a horizontal conveyor and from said horizontal conveyor to a further vertical conveyor for transporting the circuit boards back to the feed plane and to a discharge portion. In the prior-art heating apparatus, the heating portion is arranged in the transportation direction of feed portion and discharge portion between said portions. The two vertical conveyors and the horizontal conveyor connecting said vertical conveyors form a transportation device for the circuit boards through the heating portion. The heating portion serves, for instance, to remelt solder paste, i.e. for so-called reflow soldering, for curing adhesives for attaching components to the circuit board, for drying varnish on the circuit board, or the like.
The heating apparatus which is already known from practice has a relatively great constructional height, since the two vertical conveyors of the heating portion extend upwards relative to the feed and discharge portions. Moreover, the dimension of the prior-art heating apparatus in the transportation direction is relatively great, since the heating portion is arranged in the transportation direction between feed portion and discharge portion.
Furthermore, as becomes apparent from the known heating apparatus, a corresponding heating device is required for the heating portion for producing corresponding temperature profiles along the vertical conveyor and the horizontal conveyor. For instance, during heating by an air flow, many air supplies are required along the vertical conveyors with different temperatures of the air flow. A control of the air flows is relatively complicated for maintaining, for instance, a corresponding temperature profile in the upwardly transporting vertical conveyor in consideration of the rising, heated air. Moreover, venting devices with a corresponding control must be provided for air flow control, in particular, in the area of the horizontal conveyor which connects the upper ends of the vertical conveyors. The above-mentioned expensive and complex control and supply or discharge of hot air apply analogously to inert gases.